“…As is well known, pioneered by the work of Mandelbrot et al (1984), the fractality of fracture surfaces in various kinds of materials such as concrete (Saouma et al, 1990;Saouma and Barton, 1994), steel (Mandelbrot et al, 1984;Underwood, 1986), ceramic (Mecholsky, 1989) and rock (Krohn and Thompson, 1986; Radlinski et al, 1999) has been verified experimentally, which has gradually lead to the establishment of the emergent fractal fracture mechanics over the past three decades. Naturally, it is a reasonable desire that some important physical concepts or parameters in the classical fracture mechanics can be extended directly into the fractal one but, unfortunately, this is not the case sometimes.…”